According to technical development and an increase in demands regarding mobile devices, demands for secondary batteries as an energy source are rapidly increasing. Generally, nickel cadmium batteries or hydrogen ion batteries have been used as secondary batteries, but recently, lithium secondary batteries that have very low self-discharge rates, have high energy densities, and are freely charged and discharged because a memory effect is barely generated compared to nickel-based secondary batteries are widely used.
Such a lithium secondary battery mainly uses a lithium-based oxide and a carbon material respectively as a positive electrode active material and a negative electrode active material. The lithium secondary battery includes an electrode assembly, in which a positive electrode plate and a negative electrode plate on which the positive electrode active material and the negative electrode active material are respectively coated are arranged with a separator therebetween, and an exterior material, i.e., a battery case, that seals and accommodates the electrode assembly with an electrolyte.
The lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed therebetween, and an electrolyte, and is classified into a lithium ion battery (LIB), a polymer lithium ion battery (PLIB), or the like based on which positive electrode active material and negative electrode active material are used. Generally, an electrode of the lithium secondary battery is formed by coating the positive or negative electrode active material on a current collector, such as an aluminum or copper sheet, a mesh, a film, a foil, or the like, and then drying the positive or negative electrode active material.
Generally, the secondary battery has a module structure as unit cells are stacked on each other, and such a plurality of modules may be stacked on each other to form a battery pack. The battery pack may be used as an energy storage device, and is configured to prevent risks caused by external physical factors and to satisfy installation environments or installation conditions. Such a battery pack is usable for various purposes, for example, domestic use or industrial use, and if required, the battery pack may be transported or moved to a predetermined space to be used. In this case, the battery pack needs a handle for easiness of transportation or movement.